The research proposed has as its primary goal the construction of a statistical simulation model for the study of the development and spread of the AIDS epidemic within a heterogeneous population. With such a model it will be possible to predict the course of the epidemic, measure the variability of the prediction, and assess the sensitivity of the outcome to parameters in the model, particularly those that can be modified through intervention programs. The statistical model to be developed will dynamically estimate the development of the AIDS epidemic within a homogeneous group. The procedure to be used will start with the form of one common deterministic model, express time transitions as a stochastic rather than deterministic progression, and incorporate uncertainty about model parameters into the model formulation. The model for a whole region can then be obtained by aggregating over its homogeneous component parts, at the same time accounting for interaction between the groups.